Phineas Orlando Avery (1838-1916), of Earl, LaSalle County, Ill., enlisted as a private in Co. I, 4th Ill. Cav., on Sept. 4, 1861, and mustered out as a corporal on Nov. 4, 1864. His unit served in Tennessee and Mississippi, including at Shiloh, Apr. 6-7, 1862. After the war, Avery moved to Richardson County, Nebr., and lived near the town of Humboldt.

Otto Kotouc, of Humboldt, Nebr., loaned the diary to the Nebraska State Historical Society for filming in 1984, and Mrs. Nelli L. Avery, also of Humboldt, loaned the letters to the Society for filming in 1956. The Society donated the collection to the University of Illinois Library in 2009.